贵州下寒武统黑色页岩稀土元素组成及示踪特征研究

REE Composition and Tracing Characteristics of Lower Cambrian Black Shale in Guizhou

通过对贵州省织金、凤冈、开阳、天马、天星、大方等地下寒武统牛蹄塘组以及大方下志留统下部龙马溪组进行化学分析,研究常微量元素特征和稀土元素组成及示踪特征,结果表明,研究区黑色页岩化学成分以SiO2为主,其次为Al2O3、Fe2O3和K2O;微量元素中As、Mo、Pb、W等富集最为明显,以Mo、Pb、Co等含量最高。V/Cr、Ni/Co等比值表明黑色页岩多形成于贫-缺氧沉积环境,局部存在弱氧化条件;稀土元素属轻稀土富集、重稀土相对亏损型。研究区黑色页岩形成于大陆边缘区还原海水沉积并伴有热水沉积参与的环境,物质来源受陆源和幔源、深部物质加入控制。

Through chemical analysis of black shale of the Early Cambrian Niutitang Formation and the Lower Silurian Longmaxi Formation in Zhijin, Fenggang, Kaiyang, Tianma, Tianxing and Dafang, Guizhou province, the characteristics of the main and trace elements and the composition of rare earth elements were studied. It is concluded that the chemical composition of black shale in the study area is mainly SiO2, followed by Al2O3, Fe2O3 and K2O;As, Mo, Pb, W are most enriched in trace elements, the contents of Mo, Pb, Co are the highest. The V/Cr and Ni/Co ratios show that black shales were mostly formed in poor-anoxic sedimentary environments and oxidized locally. Rare earth elements are light rare earth enriched and heavy rare earth relatively depleted. The black shale was formed in a reductive seawater sedimentary environment along the continental margin with the participation of hydrothermal sedimentation. The substance sources were controlled by the addition of terrestrial, mantle-derived and deep-seated materials.